A related picture display device is illustrated in the perspective view shown in FIG. 5.
In FIG. 5. 1 is a display consisting of a cathode-ray tube (CRT) or a liquid crystal display (LCD); 2 is a main-screen area, with a selected main-program or picture normally being displayed on the entire display screen of the display 1; and 3 is a sub-screen area which corresponds to a predetermined geometrical shape and is at a predetermined location of the display, for example, at the lower right-hand corner of the main-screen, with a selected sub-program being able to be selectively displayed within the sub-screen area to overlap a display of the selected main-program.
Reference numeral 4 is a display control device which selects and controls a program or picture to be displayed in the display 1; 5A, 5B and 5C are function changeover switches provided on one of the faces, for example, the front face of the display control device 4, wherein the function changeover switch 5A corresponds to a television changeover switch for selecting television receiver pictures, the function changeover switch 5B corresponds to a video tape reproducer (VTR) changeover switch for selecting video tape reproducer pictures, and the function changeover switch 5C corresponds to a video laser disk (LD) reproducer changeover switch for selecting laser disk reproducer pictures.
Reference numerals 6A, 6B and 6C are indicators which, for example, illuminate or otherwise change in appearance (e.g., a LCD) to indicate which of the function changeover switches 5A, 5B and 5C has been selected; 7 is a picture-in-picture (P/P) changeover or selector switch which can be selected to display or erase the sub-screen area 3 of the display 1 within the main-screen 2; and 8 is a P/P changeover indicator which, for example, illuminates or otherwise changes in appearance (e.g., a LCD) to indicate that the operation of the changeover switch 7 has been selected.
Next, the operation of the related device will be described using an example.
First, when a television receiver picture is selected by operating the function (i.e., television) changeover switch 5A, a television picture received via a television receiving tuner (not shown) is displayed on the main-screen 2 of the display 1.
At this time, the indicator 6A corresponding to the function changeover switch 5A is turned on (i.e.. illuminated or otherwise changed in appearance) indicating that the picture displayed on the main-screen is a television receiver picture.
Next, by depressing the P/P selector switch 7, a selection is made to operate in a picture-in-picture mode of operation, and thus to display a sub-program or picture on the sub-screen 3 to overlap a portion of the main-screen 2.
As a result of this selection, on the sub-screen 3 there is displayed a television receiver picture which is the same as television receiver picture in the main-screen 2, and the changeover indicator 8 is turned on (i.e., illuminated or otherwise changed) to indicate that the changeover switch 7 is operated to select a picture-in-picture function.
To change the sub-program or picture selected for display on the sub-screen 3 to one which is different from the main-program or picture on the main-screen, then one of non-selected function changeover switches 5B and 5C (a non-selection being indicated, for example, by unlit indicators 6B and 6C, respectively) can be depressed to select one of video tape reproducer (VTR) pictures or video laser disk (LD) reproducer pictures, respectively, For example, when the function (i.e., VTR) changeover switch 5B is depressed, a video tape reproducer picture is displayed on the sub-screen 3, and the indicator 6B is turned on.
Further, to change the main-program or picture selected for display on the main-screen 3, the changeover switch 7 is depressed again, as a result thereof, the sub-screen 3 is turned off and at the same time the indicator 6B and the changeover indicator 8 are turned off also, leaving the main-program or picture being displayed on the main-screen 2 or display 1 alone.
As a result of the foregoing deselection of the picture-in-picture function or mode of operation, the main-program or picture selected for display can again be changed. For example,when a desired function (i.e., LD) changeover switch 5C is depressed, a picture from the video laser disk reproducer is displayed on the main-screen 2 and the indicator 6C corresponding to the function changeover switch 5C is turned on to indicate that it is a video laser disk reproducer picture which is currently selected and being displayed as a main-program or picture.
With the related picture display device being constructed as described, the picture-in-picture function or mode of operation has to be deselected, or in other words, the sub-screen 3 has to be cleared in order to change a main-program or picture which is currently selected for display on the main-screen 2. Accordingly, there has been an inconvenient drawback that it is not possible to change the main-screen 2 while watching the sub-screen 3.
In addition, when the sub-screen 3 is to be changed while the picture-in-picture function or mode is selected, there has been a problem in that, since indicators corresponding to the main-screen 2 and the sub-screen 3 are not provided separately with respect to the function changeover switches, it is not possible to tell or discern which one of the programs or pictures of the functional changeover switches 5A-5C the main-screen 2 corresponds to, and which one of the programs or pictures of the functional changeover switches 5A-5C the sub-screen 3 corresponds to.